Writing instrument



FIG. 1 is a front perspective view of a writing instrument showing my new design;

FIG. 2 is a front elevational view;

FIG. 3 is a left side elevational view;

FIG. 4 is a front elevational view with the clip member rotated 180 degrees and the writing tip exposed; and,

FIG. 5 is a left side elevational view of FIG. 4. 

The ornamental design for a writing instrument, as shown and described. 